Halogen-containing thermosetting epoxy resin



United States Patent 3,294,742 HALOGEN-CONTAINING THERMOSETTING EPOXY RESIN Bart J. Bremmer, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Filed May 10, 1961, Ser. No. 108,993 7 Claims. (Cl. 26047) The invention concerns new compositions of matter and more particularly to relatively high molecular weight curable epoxy resin compositions containing halogen atoms which impart fire-retardant properties thereto. Such resins will be referred to broadly as being epoxy resins, both in the uncured and cured state, although no epoxide or oxirane groups generally exist in the completely cured resin.

There has long been a need for an epoxy resin of superior physical properties which also has superior fireretardant properties and especially for such resin which is sufficiently fire-retardant to qualify as self-extinguishing in accordance with A.S.T.M. Test 635-56T. Broadly the term self-extinguishing means not combustible in the absence of direct continuous contact with an open flame.

A number of attempts have been made to impart fireretardant properties to epoxy resins. For example, some chlorine has been left on the alk-ane carbon atoms of a glycidyl ether of a polynuclear bisphenol when reacting such bisphenol with epichlorohydrin, by only partially dehydrohalogenating the chlorohydrin ether formed in the reaction.

Full benefit of the halogen atoms in imparting fireretardant properties to epoxy resins appears to remain unrealized when the halogens are attached only to the alkane carbon atoms comprising the carbon chain of the epoxy resins. It has also been observed that an epoxy resin wherein only halogenated bisphenols are employed is not economical and mere physical mixtures of epoxides of halogenated bisphenols and unhalogenated bisphenols are not fully satisfactory.

The principal object of the invention is to produce a self-extinguishing epoxy resin of high physical properties without accompanying adverse effects on desirable physical properties and which can be economically produced without appreciable outlay beyond conventional epoxy resin-making equipment.

A related object is to provide a new polymer containing a controlled proportion of halogenated phenolic groups therein. Other objects of the invention are to provide a resin composition which, in the uncured state, is less viscous and has longer pot life and which, in the cured state, is more resistant to acid attack and has greater strength and fiexural properties than is commonly found in resins having some resistance to burning. How the invention attains these and related objects is made clear in the ensuing description and is defined in the appended claims.

We have now discovered that, by reacting a bisphenol preferably a brominated bisphenol, e.'g., isopropylidenebis(2,6-dibromophenol), with an epoxy novolac, a polyepoxide, a diepoxide, or diepoxide ether or higher molecular weight diepoxide polyether, prepared by epoxylating a polyhydroxy alcohol or polyhydroxy phenol, or of such polyhydroxy alcohol or phenol previously halogenated (necessarily brominated if the bisphenol is not), in amounts which provide at least about 12 percent by weight of bromine in the cured resin (but which do not provide an excess of phenolic hydroxyl groups over the oxirane groups present in the epoxide or epoxide ether), a self-extinguishing resin of superior physical 1.5 to 2 oxirane groups per molecule.

3,294,742 Patented Dec. 27, 1965 ICC properties .is produced. In practicing the invention, it is to be observed that the ratio of phenolic hydroxy groups to oxirane groups must be less than 1. When an epoxy novolac (as hereinafter more fully described) is employed, the ratio of hydroxyl groups on the bisphenol to the oxirane groups of the epoxy novolac should be between 0.1 and 0.25.

The invention, accordingly, is (I) a new composition consisting of the reaction product of (A) a polyepoxide including simple or unetherized diepoxides, diepoxide ethers, higher molecular weight diepoxide polyethers, novolac polyepoxide ethers, and such diand polyepoxides and ethers thereof containing halogen substituents, (B) a bisphenol (at least one of (A) or (B) having bromine substituents attached directly to a phenolic nucleus), and (C) a hardening agent, e.g., an amine, (II) the resulting cured resin, and (III) a method of making such resin. Reactants (A) and (B) identified above, are employed in a ratio to provide an excess of (A). A ratio which provides between 0.1 and 0.9 equivalent weight of phenolic hydroxyl groups per equivalent of oxirane groups is preferred. The (A) and/or (B) reactants containing bromine-substituted phenolic rings must be employed in an amount sufficient to provide at least about 12 percent by weight of bromine in the cured resin composition. Hardening agent (C) is preferably one which enters into chemical reaction with reactants (A) and (B) to form cross-links and is employed in an amount suflicient to provide between about 0.5 and 1.5 equivalent functional atoms per oxirane group and preferably substantially the equi-equivalcnt amount thereof. For example, an amine which provides about one equivalent amine hydrogen atoms per oxirane group is preferred.

The time required for cure, i.e., to convert the deformable composition to a thermoset solid resin, varies with the specific components, the amounts thereof employed, and the temperature of cure. Although a temperature of from room temperature, or below, up to about 200 C. may be employed, the temperature recommended is between about 50 C. or somewhat higher, up to about C.

It is to be understood that the resin composition of the invention may also be made by reacting a tetrabromobisphenol with a halogenated phenol or diepoxide or diepoxide ether of a polyhydric phenol as well as by reacting it with an unhalogenated polyepoxide, polyepoxide ether, or diepoxide ether. It is also under stood that an unhalogenated bisphenol may be employed with a brominated diepoxide or diepoxide ether and further understood that a mixture of a brominated bisphenol and an unhalogenated bisphenol may be reacted with a polyepoxide or diepoxide ether (which may or may not be halogenated) to provide the composition of the invention, so long as sufficient brominated phenol or brominated polyepoxide or brominated polyepoxide ether is present to provide at least about 12 percent by weight of bromine in the final cured resin.

Bisphenol, as the term is used herein, refers to methyl diphenol and alkylidene and cycloalkylidene diphenols, illustrative of which are 4,4-isopropylidenediphenol, known as bisphenol A; 4,4'-isobutylidenediphenol, known as bisphenol B; 4,4"-methyldiphenol, known as bisphenol F; and cyclohexylidenediphenol. The term, halogenated bisphenol refers to any such bisphenol having halogen atoms attached directly to carbon atoms of a phenolic nucleus. The term diepoxides as used herein, includes epoxides having somewhat less than an average of 2 oxirane groups per molecule, e.g., those having from For simplicity of expression the term hereinafter will sometimes be used to mean both the simple diepoxides and diepoxide ethers and polyethers. Of the diepoxide ethers and higher mo lecular weight diepoxide polyethers useful in the invention, the following are illustrative:

1) The diepoxide ether of polyoxypropylene glycol having the formula:

CI\12/-CHO (lJHzCH OHzOE7CH2 0 L011; J 0 wherein n is from 0 to about 40.

(2) The diepoxide ether of a bisphenol including higher molecular weight polyethers having the formula:

The composition resulting from the reaction of (A) and (B), as defined above, has the following formula:

wherein R is H or CH and R is H, CH or C H and n has a value of from 0 to about 10. The diepoxide ethers and polyethers employed usually have an epoxide equivalent weight (i.e., a weight of resin necessary to yield 1 equivalent oxirane group) of from about 174 to about 1000; D.E.R. 332, having an epoxide equivalent weight of 174-179, and D.E.R. 664, having an epoxide equivalent weight of between 875 and 975, is illustrative; an epoxide equivalent Weight of less than 575, e.g., that of D.E.R. 661, is preferred, (3) An epoxy novolac having the formula:

6 LV 1. wherein n may vary from 0 to about 4, but is usually 1 or 2. 'In practice, when an epoxy novolac is employed, It usually has an average value of from 0.5 to 2.5, and more often of 1.2 to 1.4, thereby making a usual total average number of oxir-ane groups per molecule of from 3.2 to 3.4.

The unetherized epoxides for use in the practice of the invention include well known diepoxides among which are vinylcyclohexene dioxide and dicyclodiepoxycarboxylates, illustrative of the letter being 3,4-epoxy-6-methylcyclohexylmethyl 3,4 epoxy 6 methylcyclohexanecarboxylate having the formula:

A simple or unetherized diepoxide may be prepared by known methods, one of which consists broadly of reacting a diolefin, e.g., vincyclohex-adiene, with an oxidizing agent, e.g., peracetic acid.

The brominated bisphenol which is reacted with the polyepoxide usually has the general formula:

Br Br Br Br wherein R and R independently represent H or the lower alkyl group indicated above.

"H, CH,

glycol or polyglycol with epichlorohydrin in the presence of a Lewis acid catalyst to produce chlorohydrin and thereafter dehydrochlorinating the chlorohydrin to reform oxirane groups. Generally a polyepoxide ether of a polyhydric phenol is prepared by admixing epichlorohydrin with the phenol, e.g., 4,4'-isopropylidenediphenol, in a 4 to 6 molar excess of the epichlorohydrin, and adding NaOH slowly thereto until a slight molar excess thereof is added. The higher molecular weight polyethers are usually prepared by either adding epichlorohydrin slowly to a mixture of polyhydric phenol and NaOH up to a molar ratio of epichlorohydrin to phenol of not over about 2 and frequently less than 1, or adding a polyhydric phenol to the lower molecular weight diepoxide ether prepared above.

According to the two-stage procedure, the b-rominated bisphenol and the diepoxide ether and/ or polyether are admixed in a suitable reaction vessel, provided with heating and evacuating means, stirrer, thermometer, and nitrogen gas inlet. The contents of the vessel are stirred and heated to a maximum temperature of between about 60 and 10 C. to provide a substantially homogeneous mixture. It is thereafter cooled to between about 50 and C. and an epoxylating catalyst, e.g., a tertiary amine, admixed therewith. The second stage consists of slowly raising the temperature (at a rate of less than 5 C. and preferably about 2 C. per minute) to a temperature between about C. and about 180 0., preferably about C. and held at that temperature for about 5 to 25 minutes, usually about 10 minutes, and thereafter, without cooling, applying a vacuum, e.g., one of about 2 mm. of Hg or less, for about an additional 15 minutes to remove volatile materials. Nitrogen gas is then allowed to flow in until at least about normal pressure and temperature are established. The resinous produce so made is then removed.

According to the one-stage procedure, the brominated bisphenol and NaOH, the latter as an aqueous solution and preferably in about an equimolar proportion to the bisphenol, are placed in a suitable reaction vessel, provided with a refluxing column and heating and stirring means, and heated to between about 80 and 100 C. until the bisphenol is fully dissolved in the aqueous solution of NaOH. The solution so made is then usually cooled until some of the bisphenol tends to precipitate which is below about 45 C. and epichlorohydrin, dissolved in an inert organic solvent, is added rapidly thereto. The epichlorohydrin is employed in an amount sufficient to provide between about 0.55 (at least in excess of 0.5) and 2.0 oxirane groups per hydroxyl group in the bisphenol. The resulting mixture is then heated again to between about 80 and 100 C., accompanied by stirring. The stirring is then stopped and the mixture allowed to stratify, whereby the aqueous layer becomes the top layer and the resin composition becomes the lower layer. Separation is then effected by known separation means and the resin washed with water until it is substantialy free of OH and Cl ions. It is then dried, at, say about, 160 C., preferably at a reduced pressure.

Examples 1 to 16 below illustrate the practice of the invention employing the two-stage process.

EXAMPLE 1 1,011 pounds of the 'diglycidy-l ether of bisphenol A having an epoxide equivalent weight of 186 were placed in a 300-g-allon reaction vessel of the type above described. Stirring was started, a nitrogen 'gas blanket provided, and heat applied to raise the temperature of the contents of the vessel to 70 C. 489.5 pounds of tetrabromobisphenol A were then charged into the reaction vessel and intermixed with the diglycidyl ether therein. The reaction mixture was then heated to 104 C., while being continually stirred, and maintained at that temperature until a substantially homogeneous reaction mixture was obtained. Thereafter, the contents of the vessel were cooled to 70 C. and about 2.8 pounds of triethylamine were admixed with the contents of the vessel. The temperature was again raised to about 105 C., and thereafter allowed to continue to rise, due to the exothermic heat of reaction, to a temperature of about 145 C. (The triethylamine is added for the purpose of improving the expoxylation process and is insufficient to effect a cure, i.e., convert the composition to a thermoset resin.) The reaction mixture was then further heated to 165 C. and held at that temperature for about 30 minutes while a vacuum was applied to remove volatiles from the reaction vessel. The vessel was then cooled to room temperature and the resinous pro-duct thus made removed therefrom. The product was analyzed and showed the following properties:

Percent yield A portion of the resin so made was dissolved in methyl ethyl ketone (MEK) to produce an 80% solution thereof, calculated on the weight of non-volatiles in the resin. The MEK solution showed the following properties.

Property: Value Absolute viscosity, at 25 F cps 3,120 Gardner viscosity, at 25 F. Y-Z Gardner color 6-7 EXAMPLE 2 886 pounds of a diglycidyl ether of bisphenol A having an epoxide equivalent weight of 189 were placed in a reaction vessel of the type above described, heated to about 70 C., and 618 pounds of tetrabromobisphenol A admixed therewith. The temperature was then raised to C., accompanied .by stirring. When the mixture was substantially uni-form, the temperature was dropped and about 2.8 pounds of triethylamine were admixed with the contents of the vessel. The temperature was again raised to about 100 C. and allowed to continue to rise, due to exothermic effects, to about C. It was thereafter further raised to about C. I The flow of nitrogen gas was then discontinued and a vacuum applied to the vessel for 45 minutes while the contents thereof were held at between 175 and C.; it was then cooled. The resin thus made was analyzed and shown to possess the properties set out in the table below.

Property: Value Epoxide equivalent weight 751 Durrans softening point C 101 Percent Br (calculated) 24.2 Percent Br (determined) 25.3 Hydrolyzable chlorine percent 0.12 Molecular weight 1340 Specific gravity 1.4410 Yield 1bs 1495.5 Theoretical yield 1505 Percent yield 99.2

Portions of the resin so madewere admixed with MEK to give the percent solids, based on the non-volatiles, set out below. The MEK solution possessed the following characteristics:

Properties and Values Obtained Percent nonvolatile solids in MEK Absolute Gardner Gardner Viscosity at Viscosity Gardner Color 25 (3., eps.

so 19, 200 3, 700 X-Y 6-7 650 P-Q 6-7 Portions of the resin composition prepared in Example 1 above were admixed with various curing or hardening agents set out in Examples l-A to 1-D below:

EXAMPLE 1-A To one portion of the resin composition of Example 1 were admixed 3 parts per 100 parts by weight of resin composition, of BF zmonoethylamine complex. The resulting curable mixture was admixed with acetone in an amount of about 50% for use in impregnating cloth. The cloth employed was #181 style, Volan A finish. Substantially equal size sections of the cloth were impregnated and laid in tiers or nested according to known practice, to make a 12-ply laminate. The resin constituted 42.4 percent by weight of the weight of the laminate as assembled. The laminate was placed in an oven at about 163 C. for 8 minutes. The resin was somewhat tacky but the laminate could then be easily handled. It was then placed in a press under a pressure of 40 pounds per square inch (p.s.i.) and cured at 325 F. (ca. 163 C.) for 1 hour. About 9.9 percent of the resin was caused to exude from the laminate leaving a resin content of 32.5 percent by weight of resin. The laminate was then post cured at 350 C. (ca. 177 C.) for-2 hours. The laminated cloth article so made was 108 mils (0.108 inch) thick. It was flexible and possessed good drop characteristics. It was subjected to standard A.S.T.M. tests and gave the values set out below:

Flexural strength at 75 F. (ca. 24

C.) 85,500 p.s.i. Flexural strength at 300 F. (ca.

149 C.) 12,800 p.s.i Wet fi-exural strength (after 2 hrs. in

boiling H O) 79,000. Edgewise compression strength 52,000. Tensile strength 51,300.

7 Tensile modulus 1.2X1O Electrical propertyzvolume resistivity for 1 minute (condition A) Percent water absorbed (2 hrs. in

1.4)(10 ohm-cm.

gelled in minutes. The laminate was then press-cured at 325 F. at a pressure of 60 p.s.i. for 1 hour and thereafter given a post cure of 2 hours at 350 F. The final laminated cloth article was 107 mils thick and has a boiling water) 0.217. 5 resin content by weight of 31 percent. The laminate was Flammability Self-extinguishing. tested and showed the following results:

EXAMPLE 1 1 l i iit t Z35 3533 i exura s ren a p. .1. To a second portion of the resin of Example 1 was Wet flexural Strength (after 2 hours admixed a combined hardening agent consistlng of 5.2 in boilin Water) 88 000 p s i parts by weight of methyl nadic anhydride, 28 parts by Edgewise i gf g i;' 55000 weight of hexahydrophthalic anhydride, and 2 parts by T ensile strength 48,500 p.s.1. weight of benzyldimethyl amine per 100 parts of resin. Tensile modulus 122x106 The curable mixture was admixed with acetone to make Electrical p p z ggxg l g'f g g i a 50 percent by welght composition suitable for impregtivity for 1 minute (Condition A) 56X1013 nating cloth. Sections of the same cloth employed above Flammabflit Se1f extin guishing were impregnated and laid in tiers to make a 14-ply y u laminate. The resin comprised 37.6 percent of the EXAMPLE 1-D Weight of laminate as assembled T resin lami' Another portion of the resin composition prepared in nant gelled In 100 e The lamlnate was y Example 1 was admixed with dicyandiamide in an Placed 111 a Press, sublected to a Pressllre of 100 P- amount by weight of 6 parts per 100 parts of the resin and h at d at 325 F- f 0- 110111 followed y a P composition. Cloth sections were impregnated and a Cur of 16 h urs at 32 e lammated 8111016. Was laminated cloth article was made similarly as above de- 145 m11s thick and m P Percent f the finls hed scribed and tested. It showed comparable properties to lamltlate- The lamllfated al'tlcle Was Strong and flexlble- 5 the articles cured above and was particularly marked in It was tested according to standard A.S.T.M. tests and its resistance to burning according to A.S.T.M. Test gave the values set out below: D-635-56T. Flexural Stmngth at F. 81,370 Psi Examples 3 to 15 of the invention were run, follow- Flexural strength at (1 111g generally the two-stage procedure employed 1n the hour) 9,170 psi preceding examples. Bisphenol A and a diepoxlde ether Wet flexural strength (after 2 hours were heated, with stirring, to about 110 C. to obtain in boiling Water) 76,860 a substantially uniform mixture and then cooled to about Edgewise compressivfi Strength 6630a 80 C. Between about 0.1 and about 0.5 percent of tri- Tensile modulus ethylamine was then admixed therewith. The reaction Flammability sdfiextinguishing' mixture was then raised to about 165" C. and, after about 25 minutes at that temperature, during the last portion EXAMPLE of which a vacuum was applied to remove volatile ma- A third portion of the resin composition of Example 1 terial, the mixture was cooled and the vessel swept out was admixed with methylene dianiline in an amount of with nitrogen gas. The resin so made was then removed 10.5 parts per 100 parts of resin composition. The reand tested. The ingredients and amounts thereof emsulting mixture was admixed with acetone to make a ployed, together with physical properties of the uncured percent by weight fluid composition especially suitable resin, are set out in Table 1 below:

Table I Polyhydric Phenol Diepoxide or Ether Physical Properties Example Number Epoxlde Equlv. Wt. Gardner Values Amount Amount Durrans Percent Type in Type in Softening Br grams grams Calculated Actual Point Of 75 In MEK Color Viscosity 3 Tetrabromo- 27.2 Diglycidyl ether of tetra- 350 420 449 79.1 47.1 10-11 A bisphenol A. bromo bisphenol A. 4 .d0 350 506 538.2 90.6 47.8 10-11 (J 5--- 350 765 787. 8 114. 5 49. 0 s" 350 466 497.0 87.5 43.5 8 A-B 7-- 350 550 582. 9 9s. 2 42. 4 D-E 8-- rl0 350 077 688.8 103.6 40.7 10-11 T-U 9 TetgggliOROblS- 350 484 502 90.0 42.6 10 A 10 Tejgzggtfrxobis- 81.6 Epoxide 201 150 330 374 86.3 20.0 12-13 H 0 l 108.8 Dlglycirlylethcr ottetra- 285 055 706 94.0 10.1 7-8 S chloro bisphenol A. do 108.8 do 221 547 041.1 102.1 19.1 5-6 Y 13 do 81.6 Diglytiidyl ether ofresor- 128 299 310 39.7 22.5 8-9 OlHO 14 BisphenolA 34.2 Diglycidyl ether of 4,4'- 452 695 826.5 103.5 38.7 14 F-G cyclohexidene bis (2,6- dibromophenol) 15 iggggg gg g f tetra- 1-6 580 612.4 92.1 41,7 1445 13-13;

2 Epoxide 201 is 3,4-epoxy-fi-methylcyclohexylmethyl-3,4-epoxy-G-methylcyclohexanecarboxylate.

for impregnating purposes. Sections of the same 181 style, Volan A cloth employed above were impregnated with the acetone-resin composition and laid in tiers to make a 12-ply laminate. The resin comprised 37 percent by weight of the laminate as made. The laminate The uncured resins of Table I are more readily diluted in organic solvents than known epoxy resins, thereby providing low viscosity compositions for more convenient application. Representative specimens of resins of the type made by curing the resin compositions of Table was placed in 325 F. temperature. The resin laminant I were strong, flexible, and self-extinguishing.

9 EXAMPLE 16 To show the use of an epoxy novolac in the practice of the invention, 177 grams (providing 1 gram equivalent) of an epoxy novolac, having an average of between 3.2

when an epoxy novolac having an oxirane functionality of more than 3.4 is used, a lower ratio of hydroxyl groups may be employed.

EXAMPLES 17-18 5 an i g g groups P molecgfle g 5 i v Examples were run accordmg to the one-stage procegrovl g f W 3 0 t i dure described above. In these examples, a charge of mlxe m a Santa e re actlon vesse. the bisphenol and an aqueous solution of NaOH was put Wlth t f f con enser" mtrogen gas mlet an in a reaction vessel equipped, as required, for heating and g and Snmng means' Tue Vessel was flushed refluxing. The charge was heated while being stirred, Wlth mtrogen and the contents then brought to 165 at about 80 C., to dissolve the bisphenol in the aqueous over a Penod of 1 hour we Surfer then started and solution. It was thereafter cooled to below about 45 C. m f then held t temperate for 3 P and epichlorohydrin, in some instances admixedwith an mamtammg moderate swung The resm of the mven' inert solvent, admixed therewith. The resulting mixture tron was thereby formed. The vessel was cooled an was refluxed, while being stirred, at about 80 C. for about the resin remoYed a bntfle f The had a 80 minutes. Stirring was then discontinued whereupon Durran S Sofiemng P of and a bromme the contents of the vessel stratified into an upper aqueous tent of p l The @5111 was Subsequently layer and a lower organic layer containing the epoxylated melted and portions thereof admixed w1th such hardenbi h L Th lower layer was Separated and watering agents as primary and secondary amines or dicarwashed until it was substantially free of Cl and OH ions. boxylic acids in amounts suificient to provide about 1 The reactants, the amount employed, and properties of reactive hydrogen or carboxyl group (dependent on the the uncured resin obtained are set out in Table II.

Table II Polyhydric Phenol Physical Properties Example NaOH in Epichloro- Organic Number grams 1 hydrin in solvent in Amount in grams grams Epoxy Equl- Durrans Gardner Type grams valent Weight S.P.,

Br Color V15 17 Tetrabromobis- 272 38.2 83.25 Toluene, 50. 731.5 88.8 47.9 9-10 13-0.

phenol A. 18 BlsphenolA 85.5 31.4 69.4 .do 664.4 91.7 21.1 11-12 T-U.

Tetrabromobls- 68. 0

phenol A.

9 All resins were seltextinguishing according to A.S.T.M. Test D635-56T.

hardening agent used) per oxirane group present. Thermoset resins of good strength and flexibility and which were self-extinguishing can be made by admixing amine type or dicarboxylic acid type hardening agents with the reaction product of epoxy novolacs and a brominated bisphenol as was made in this example. The cured resins so made have excellent strength and flexural properties and are self-extinguishing. A number of curing agents may be used, e.g., cured epoxy novolac resins customarily result in a heat distortion temperature of from to centigrade degrees above that of cured epoxy resins which are made by employing a bisphenol. This desirable physical characteristic of epoxy novolac resins is due to the higher functionality thereof.

If desired, a catalyst for epoxylation may be employed in the reaction mixture of the epoxy novolac and brominated bisphenol. A catalyst recommended is a tertiary amine, e.g., triethyl amine, in amounts up to 2 percent by weight of the reaction mixture. The catalyst is conveniently removed at the close of the reaction period by Reference to Table II shows that resins of the invention made according to the one-stage procedure possess good strength properties, have excellent Durrans softening point values, and are self-extinguishing.

The uncured resin of the invention has been shown to have a lower viscosity in organic solvents, longer pot life, and better acid resistance than conventional resins.

The cured resin of the invention compares favorably with known epoxy resins in strength and flexural properties. In addition thereto, the cured resin is self-extinguishing and has better resistance to corrosivity when in contact with aqueous acid solutions. The species employing the epoxy novolac resins have a desirably high heat distortion value appreciably above that of comparable epoxy resins.

Having described my invention, what I claim and desire to protect by Letters Patent is:

1. A composition of matter consisting of the reaction product of component (A) a polyglycidyl ether having the formula:

vacuum distillation. Best results are obtained, when a bisphenol and an epoxy novolac of the type employed in LV I wherein n may vary from O to about 4, and component (B) 2,2-bis(3,S-dibromo-4-hydroxyphenyl)propane, at

Example 16 are present in an amount to provide between least 1 of components (A) and (B) containing bromine 0.1 and 0.25 equivalent hydroxyl groups in the bisphenol per equivalent oxirane group in the epoxy novolac. When an epoxy novolac having an oxirane functionality of less than 3.2 is used, a higher ratio of hydroxyl provided substituents directly attached to a phenolic nucleons thereof, in an amount by weight of components (A) and (B) to provide at least 0.1 and less than 1.0 equivalent weight of hydroxyl groups of component (B) per equivalent by the bisphenol may be employed, and, on the other hand, 7 weight of oxirane groups of component (A) and a suf- 1 1 ficien-t amount of the component containing bromine-substituted phenolic nuclei to provide at least 12% bromine by weight of said composition.

2. The composition of claim 1 wherein component (A) contains an average of between about 3.2 and 3.4 oxirane groups per molecule.

3. The composition of claim 1 wherein the ratio of hydroxyl groups in the 2,2-bis(3,5-dibromo-4-hydroxyphenyl) propane is between 0.1 and 0.25 equivalent weight per equivalent weight of oxirane groups present in said polyglycidyl ether of novolac.

4. A durable, high strength self-extinguishing resin comprising the heated mixture of the composition of claim 1 and a hardening agent which effects cross-linking of residual oxirane groups which have not reacted with hydroxyl groups selected from the class consisting of primary, secondary and tertiary aliphatic and aromatic amines, dicarboxylic acids and the anhydrides thereof, and boron trifiuoride and complexes thereof wherein the complexing agent is selected from the class consisting of amines, glycols, and others.

5. The method of making a self-extinguishing thermoset resin having high strength and corrosion-resistant properties consisting essentially of admixing component (A) a polyglycidyl ether having the formula:

LR) l wherein n may vary from 0 to about 4, and component (B) 4,4-isopropylidenediphenol, at least one of components (A) and (B) containing bromine substituents attached directly to a phenolic nucleus thereof, and components (A) and (B) being employed in an amount suf ficient to provide at least 0.1 but less than 1.0 equivalent weight of hydroxyl groups of component (B) per equivalent Weight of oxirane groups of component (A), and the component which contains the bromine-substituted phenolic nuclei being present in an amount sufiicient to provide at least about 12 percent bromine in the resin composition when subsequently cured; heating the reaction mixture at between about 80 and about 110 C. until it is substantially homogeneous; cooling the mixture to between about 50 and 90 C. and admixing therewith between about 0.1 and 0.5 percent by weight of a tertiary amine, while stirring; thereafter increasing the temperature of the resulting mixture at a rate not in excess of about centigrade degrees per minute until an advanced temperature of between about 120 and 180 C. is reached and holding at that temperature for from about 5 to about minutes; applying a partial vacuum, while holding at the advanced temperature, to remove the tertiary amine; flushing with an inert gas while resuming atmospheric pressure; and cooling the resulting resinous mass but, while still fluid, admixing therewith a hardening agent selected from the class consisting of primary and secondary aliphatic and primary amines, dicarboxylic acids and anhydrides thereof, and boron trifluoride and complexes thereof, wherein the complexing agent is selected from the class consisting of amines, glycols, and ethers, said hardening agent being employed in an amount sufficient to efiect cross-linking of residual oxirane groups remaining unreacted with hydroxyl groups in said resinous mass and subjecting the resin containing the hardening agent to sufficient heat to convert it to a self-extinguishing thermoset resin.

6. The method according to claim 5 wherein said resulting resinous mass prior to admixing therewith said hardening agent is cooled to a solid, the solid so made admixed with and dissolved in a liquid hydrocarbon solvent prior to admixing said hardening agent therewith, and thereafter the liquid hydrocarbon solvent containing the resin and hardening agent subjected to suflicient heat to volatilize off the liquid hydrocarbon solvent and effect cross-linking and conversion of the resultant mass to a self-extinguishing thermoset resin.

7. The method according to claim 6 wherein the liquid hydrocarbon solvent is toluene.

References Cited by the Examiner UNITED STATES PATENTS 2,615,008 10/1952 Greenlee 26047 2,658,884 11/ 1953 DAlelio 26047 3,016,362 1/1962 Wismer 26047 3,058,946 10/ 1962 Nametz 2602.5 3,093,599 6/ 1963 Mueller-Tamm et al. 

1. A COMPOSITION OF MATTER CONSISTING OF THE REACTION PRODUCT OF COMPONENT (A) A POLYGLYCIDYL ETHER HAVING THE FORMULA: 